The swallows that nested in the - what, five, six inch? - space above the hydrometer at the front door to my parents' place, under the eaves (click on the photo to enlarge). They built a nest up there once, had their babies, fed them, taught them to fly, and the nest was empty so it was taken down. Then swallows came back the next year and built another nest. I believe one year my parents kept the nest up there and swallows took up residence. The empty nest is still up there even though there were no swallows this year. Aside from the spattering of bird shit, it was really cool having them there. The parent swallows would come with their freewheel food and the fledglings would go nuts with their high chirping. It's amazing how industrious these birds are. If I remember right, they were sitting up there a number of times while me and my friend were smoking stogies and drinking beer on the porch. They didn't seem to mind. Nor we.